# 用Python的lambda来实现凯撒加密算法（右移13位）：
abc = "abcdefghijklmnopqrstuvwxyz"
rt13 = None


def test_caesar():
    s = "xthexrussiansxarexcoming"
    assert rt13(s) == 'kgurkehffvnafknerkpbzvat'
    assert rt13(rt13(s)) == 'xthexrussiansxarexcoming'
